Baghdad, Iraq (CNN) -- Two U.S. service members were killed Monday during operations in southern Iraq, the U.S. military said Tuesday.

There were no further details about the incident, and their names are being withheld pending notification of next of kin.

Violence has dropped dramatically in recent years in Iraq. Under a U.S.-Iraqi security pact, which set a timetable to withdraw American forces, U.S. troops must be out of Iraq by Jan. 1, 2012.

However, U.S. troops have increasingly been targeted by roadside bombings and mortar attacks, largely in Baghdad and southern Iraq -- a Shiite stronghold.

Five American soldiers were killed June 6, the single largest loss of life among U.S. troops since 2009, and the military says that attack is likely the work Shiite militia trying to take credit for driving forces out of the country.